This invention relates to a metal gasket for use in automobile engines, screw engines, freezing equipment, air conditioning units and the like, and to a method of producing the metal gasket.
As gaskets for automobile engines, so-called asbestos type gaskets have been widely used which are made of single, jointed or beat sheets of asbestos as sole or composite materials. Recently, however, various new types of gaskets have progressively been used in practice, which are made of metals, graphites, fibers and the like as sole or composite materials, in place of the asbestos which causes a problem of public nuisance. Particularly, metal gaskets provided on their surfaces with rubber layers are superior in performance and cost to other new gaskets in substitution for the asbestos gaskets, and are expected to be widely used in the future.
The sealing capability and durability are important among various properties required in gaskets for automobiles. It has been proposed to deposit a rubber coating layer directly on surfaces of a metal plate as a substrate in order to improve the sealing capability. In case of metal gaskets, however, the sealing capability and durability depend mainly upon the bonding power between the metal plate and the rubber coating layer. It is therefore important in manufacturing rubber-coated metal gaskets to improve the bonding power therebetween and to prevent the bonding power from lowering in use conditions.
Therefore, attempts have been made to improve the bonding power between the metal plate and the bonding layer or the rubber layer and to maintain the improved bonding power for a long period of time with the aid of an activation treatment or galvanizing which is applied to the surfaces of the metal plate.
Recently, however, high performance automobile engines have been developed and widely used so that metal gaskets are also used under more severe conditions, with the result that the durability of the gaskets has become still more important. Under such circumstances, even the above gaskets of metals coated with rubber coating layers encounter a problem of insufficient durability.